Pediatric anesthesia week 1

Question 1

What times are considered preterm, neonate, infant, and child?

Answer 1

Pre-Term – prior to 37 weeks gestational age
Neonate 1-28 days of life
Infant 28 days -1 year
Child >1 year

Question 2

Most significant part of transition occurs
within the first _____ hours after birth

Answer 2

24-72

Question 3

4 Adaptive Changes

Answer 3

Establish FRC
Convert Circulation
Recover from birth asphyxia
Maintain core temperature

Question 4

Fetal Hgb shifts oxyhemoglobin dissociation curve to the RIGHT OR LEFT?

Answer 4

To the left

[Increased O2 loading in the lungs/placenta, decreased O2 unloading at tissues]

Question 5

O2 transport is accomplished by ______ which totals ______%

Answer 5

O2 transport is accomplished by fetal Hgb which totals 70-90%

Question 6

4 Weeks

Answer 6

primitive lung buds develop from foregut

Question 7

16 Weeks

Answer 7

branching of bronchial tree complete to 28 divisions, no further formation of cartilaginous airways

Question 8

24 Weeks

Answer 8

primitive alveoli (saccules) and type II cells present; surfactant detectable; survival possible with artificial ventilation

Question 9

28-30 Weeks

Answer 9

capillary network surrounds saccules; unsupported survival

Question 10

36-40 Weeks

Answer 10

true alveoli present, roughly 20 million at birth

Question 11

Birth-3mon

Answer 11

PaO2 rises as R to L mechanical shunts close

Question 12

To 6 yrs.

Answer 12

rapid increase in alveoli 350 million at age 6

Question 13

Traditional view – ____, _____ and _____ of birth asphyxia stimulates chemoreceptors that produce gasping followed by rhythmic breathing

Answer 13

Traditional view – hypoxemia, hypercarbia and acidosis of birth asphyxia stimulates chemoreceptors that produce gasping followed by rhythmic breathing

Question 14

What allows gas exchange?

Answer 14

Increase in PO2, Decrease in CO2, Decrease in Pulmonary Vascular Resistance

Question 15

Current View – rhythmic breathing occurs with _____ of the umbilical cord and increasing O2 tensions from air breathing

Answer 15

Current View – rhythmic breathing occurs with clamping of the umbilical cord and increasing O2 tensions from air breathing

Question 16

What is the primary event of the respiratory system transition?

Answer 16

INITIATION OF VENTILATION

Changes the alveoli from a fluid-filled to an air-filled state

Large surface tension forces are overcome by the small radius of the curvature of the diaphragm

Infant must generate high negative pressure,
-70 cm H2O, to inflate the lungs

Question 17

Treu/false:

Answer 17

Neonate and infant lungs prone to collapse – weak elastic recoil, weak intercostal muscles, intra-thoracic airways collapse during exhalation

Question 18

FRC of approx. ______ ml/kg is established to act as a buffer against cyclical alterations in PO2 and PCO2 between breaths

Answer 18

FRC of approx. 25-30ml/kg is established to act as a buffer against cyclical alterations in PO2 and PCO2 between breaths

Question 19

Why don’t infants have lung collapse all of the time?

Answer 19

Infants terminate the expiratory phase of breathing before reaching their true FRC which results in intrinsic PEEP and a higher FRC. When anesthetized, however, this protective mechanism is abolished. The opposing tonic state of the intercostal muscles is ove-rridden and atelectasis occurs.

The moral of this story – PEEP of 5cm H2O can help maintain FRC/lung inflation in the neonate during anesthesia.

Question 20

______ depresses the neonate’s response to CO2

Answer 20

Hypoxia depresses the neonate’s response to CO2

Question 21

How donNewborns respond to hypercarbia?

Answer 21

by increasing ventilation

Question 22

Initial hyperpneic response is abolished by:

Answer 22

hypothermia and low levels of anesthetic gases

Question 23

True/False: Response to hypoxia is biphasic – initial hyperpnea followed by depression of respiration in about 2 min

Answer 23

True

Question 24

Hypoxia causes PROFOUND _______ in babies

Answer 24

bradycardia

Respiratory pauses exceeding 20 sec. or those accompanied by bradycardia or cyanosis

Question 25

Contributing Factors for Apnea of Infancy

Answer 25

Increased Work of Breathing = FATIGUE

Very compliant upper airway structures and ribcage which tend to collapse during inspiration

Inefficient diaphragmatic contraction

Only 25% of muscle fibers in diaphragm are Type I fatigue- resistant work horse fibers vs. adults are 55%

THEY ARE VERY CARTILAGINOUS..everything breaks down (ribcage…)

Question 26

More Contributing Factors for Apnea of Infancy

Answer 26

Increased O2 consumption 6ml/kg
Decreased FRC (non-functional residual capacity)
Increased closing volume

Question 27

Where does gas exchange occur?

Answer 27

In the placenta

Question 28

Lungs require only nutrient flow ______% of cardiac output

Answer 28

5-10%

Question 29

Fetal intracardiac and extracardiac shunts exist to:

Answer 29

minimize blood flow to the lungs while maximizing flow/O2 delivery to organ systems

Ductus Venosus
Foramen ovale
Ductus Arteriosus

Question 30

Deoxygenated blood travels the descending aorta to the umbilical arteries to the placenta (very low resistance to flow)

Oxygenated blood returns via the?

Answer 30

umbilical vein (PO2 35 mm Hg)

Question 31

Ductus venosus diverts approx. 50% of blood away from the?

Answer 31

liver into the IVC then to the RA

Question 32

Summary

Answer 32

The foramen ovale, ductus arteriosus, and ductus venosus are the shunts needed for effective fetal circulation that must close after birth to allow effective newborn circulation

Increased SVR, decreased PVR – flow through FO and DA becomes left to right, the shunts close, and circulation becomes like that of an adult

Utero – pulmonary vascular resistance high, systemic vascular resistance low

Born – systemic vascular resistance high, pulmonary vascular resistance low, shunts functionally close

Question 33

Persistent Pulmonary Hypertension of the Newborn (PPHN)

Answer 33

Persistence of fetal shunting beyond the normal transition period in the absence of a structural heart defect.

Because the shunts are not anatomically closed immediately after birth, certain clinical conditions may contribute to either the persistence of or a return to fetal circulation

HYPOXIA and ACIDOSIS

Increased PVR
Pulmonary hypertension
Decreased PBF
RAP > LAP
Increased ductal flow

This can open the foramen ovale

Question 34

Signs and Symptoms of persistent pulmonary htn of the newborn

Answer 34

Marked cyanosis
Tachypnea
Acidosis
Right to left shunt across FO and DA = marked cyanosis
(right to left = cyanotic shunt)

Question 35

Treatment of persistent pulmonary htn of the newborn

Answer 35

Hyperventilation – maintain alkalosis
Pulmonary vasodilators – prostaglandin
Minimal handling
Avoidance of stress
*ADEQUATE VENTILATION AND OXYGENATION IS KEY

Question 36

fetal kidney

Answer 36

Low renal blood flow
Low glomerular filtration rate (GFR)

Question 37

By ____ weeks all nephrons are developed, so a premature babe has incomplete renal development.

Answer 37

By 34 weeks all nephrons are developed, so a premature babe has incomplete renal development.

Question 38

First few days of life urine

Answer 38

Urine osmolarity 700-800 mOsm/L
Creatinine 0.8-1.2mg/dl

Question 39

True/false: the neonate will continue to excrete Na even in the presence of a severe Na deficit

Answer 39

True.

Immature neonatal tubules do not completely reabsorb NA under the stimulus of aldosterone

Result – the neonate will continue to excrete Na even in the presence of a severe Na deficit

The neonate is therefore considered an “obligate sodium loser”

Question 40

Urine Na

Adult 5-10 mEq/L
Neonate 20-25 mEq/L

Answer 40

Why is this so important? Because the renin-angiotensin-aldosterone system is the primary compensatory mechanism for the reabsorption of the Na and H2O losses of plasma, blood, GI tract fluid, and third space fluid during surgery

Moral of this story – choose your IV fluid with this in mind. Neonates cannot completely conserve Na, so a baby will continue to produce dilute urine to the point of dehydration without adequate fluid replacement. This fluid must contain Na!!!!

Question 41

What is the best maintenance fluid for a baby?

Answer 41

Maintenance fluid should contain glucose D5.2NS (Balanced Maintenance Fluid in a Baby)

Question 42

Do babies need blood replaced sooner vs later if blood loss happens in the OR?

Answer 42

Yes!

Higher Hgb/Hct (35% lowest acceptable) because of high O2 demand with limited ability to increase CO

Increased blood volume per unit weight

Increased cardiac output per unit weight

90 ml/kg blood volume in term baby

100ml/kg blood volume in pre-term baby

Question 43

Heat loss is governed by

Answer 43

Conduction – surface to surface, use warm blankets, bair hugger

Convection – surface to air currents, reduce air movement across body. Most OR’s for neonates kept at 80 degrees

Radiation – electromagnetic energy from the body to colder objects in the room (highest % of loss), use heat lamps and “french fry” lights

Evaporation – vaporization , cover exposed body cavities and humidify inspired gas

Question 44

What is the major component of thermal regulation in neonates?

Answer 44

Non-shivering thermogenesis

Metabolism of brown fat:

Develops in the fetus b/t 26-30 weeks gestation
Comprises 2-6% of the neonate’s total body weight
Located in the mediastinum, b/t the scapulae, around the adrenals, in the axilla
Abundant vascular supply and rich innervation of the sympathetic nervous system